I accidentally removed a library from my code while I was still using it. PyCharm did not underline the filename. Why?

Hello,

Yesterday I removed “import sys” from my code because it was grayed out and later uncommented a line containing sys.stdin.buffer.read(). I did that very fast and switched to another file before committing.

Today my colleague informed me that I broke the file by removing “import sys” and I was shocked by that fact because usually PyCham underlines the filename with a red wavy line.

The question is: Why PyCharm did not underline the file name?

I'm using PyCharm 2024.2.1 (Community Edition) on Ubuntu 24.04 LTS
Build #PC-242.21829.153, built on August 29, 2024